Carb sync for a beginner

[JerseyJon]

So this is all very embarassing for me, but here goes. I had the carbs cleaned at a shop (strike 1), got them back and put them back on the bike with new carb boots. Like you guys have said, the old ones just looked cracked on the outside, but were fine on the inside, so the new carb boots were a waste of money (Strike 2). The bike fired right up on the first try (+1 bike shop), so it was time for the sync, which is where I was two weeks ago, when I hooked up my motion pro sync tool and promptly sucked all the blue fluid out of it (Strike 3). So I made a fish tank vacuum gauge sync tool, but you guys said get a 4 gauge setup from ebay, which I did. So now I have 3 sync tools for two non-running bikes (Strike 4). I hooked up the 4 vacuum gauge tool last night at 10:45, thinking it would take 15 minutes to sync the thing (Strike 5). When I started the bike, the needles on the 4 vacuum gauges started to flutter so wildly as to be unreadable (Strike 6). I noticed that the tool came with these brass tubes that you're supposed to screw into the engine manifolds, but, as you know, the xs11 has only that barbed nipple on the boots, not a threaded nipple (Strike 7). So I tried to put the brass tubes into line between each carb and each gauge by slipping tubes over the ends, and that didn't really help; the needles were still fluttering (Strike 8). So, if I want to use that 4 vacuum gauge setup, how do I get the needles to stop fluttering so I can read them?

Please help, because I think I may be running out of strikes here.

[jetmechmarty]

Start here: Easy Bench Sync Method

See if this thread helps you: http://www.xs11.com/forum/showthread...mpening&page=3

[CatatonicBug]

I'm not entirely familiar with the tool you are using, but I believe you need to have a flow restriction on the vacuum hoses. That may be what those little brass tubes are for. On mine, I had to cut 6" off the hoses (the end closest to the engine) and insert these little 2-ended barbs in the middle, then re-connect the 6" sections to the barbs. That is what keeps the gauge from fluttering.

[Eastcoaster]

JerseyJon keep us posted I am, also new to all of this and will be looking into doing the same thing in a few days I am just south of you exit 25 off the parkway

[bikerphil]

Those brass tubes are for other bikes, they won't fit the XS11 setup. The gauges should have come with 4 plastic regulator valves with a thumbscrew that adjusts to minimize the gauge flutter.

[crazy steve]

I'm not entirely familiar with the tool you are using, but I believe you need to have a flow restriction on the vacuum hoses. That may be what those little brass tubes are for. On mine, I had to cut 6" off the hoses (the end closest to the engine) and insert these little 2-ended barbs in the middle, then re-connect the 6" sections to the barbs. That is what keeps the gauge from fluttering.

+1 on that. Some have used 'spare' pilot jets pushed into the lines, some gauge sets come with the brass tubes. However you do it, some sort of restriction is needed to 'stabilise' the gauge...

[JerseyJon]

Wow. Thanks guys. This place continues to amaze me.

Phil, the kit came with little plastic valves, but I didn't put those in the lines because I thought that doing so would take the gauges out of calibration with one another. I mean, I could put those in the lines, and crank each one down until the flutter was reduced enough to get a reading. But wouldn't that mean that the factory-calibrated gauges were now uncalibrated because each of those precisely machined plastic valves would be set somewhere different? Or am I not understanding fluid mechanics well enough?

[JerseyJon]

JerseyJon keep us posted I am, also new to all of this and will be looking into doing the same thing in a few days I am just south of you exit 25 off the parkway

Will do. Nice to see another Jerseyite here.

[crazy steve]

Phil, the kit came with little plastic valves, but I didn't put those in the lines because I thought that doing so would take the gauges out of calibration with one another. I mean, I could put those in the lines, and crank each one down until the flutter was reduced enough to get a reading. But wouldn't that mean that the factory-calibrated gauges were now uncalibrated because each of those precisely machined plastic valves would be set somewhere different? Or am I not understanding fluid mechanics well enough?

Use the valves; they'll have no effect on calibration, simply adjust each one just until the 'flutter' goes away.... If you close them too far (and gauge will start reading low), that can cause a problem. But that's why they were included, to 'steady' the gauge.

[jimbyjimb]

I think it can be pretty easy to over analyze some tasks. I'm plenty guilty of it myself, especially when new to something, everybody has to learn the hard way. That being said, I have talked to some people about syncing carbs and while I don't doubt, like anything else, that it can be somewhat difficult at times on vehicle with problems for the most part it's a fairly straightforward and simple chore. Just remember to be patient, take your time and make adjustments to carburetors very slowly.

I use the aquarium 4-way vacuum manifold and one vacuum gauge myself. Sort of like in the tech writeup, just without the buffer tube. If the needle is going nuts slowly turn the valve down until the needle is more steady. I personally want a bit of flutter in it just so I know I haven't accidentally cut off all vacuum to the gauge. In my opinion it isn't critical that all carbs be absolutely perfect. There will usually be some very minor differences, and that's just how ICE's are. So long as average vacuum is pretty close it should be good enough. My bike runs great this way getting 36-40 mpg and idling pretty steadily at 1100. Just really take your time. Sometimes you can get 1 and 2 together, 3 and 4 together, sync them all and then a minute later one is back out of sync again. It's just a matter of doing it over and over, slowly, until they all match up as best as you can manage. It should be easy to get them all under .5 in/hg differential, provided idle speed and mixtures are all ok.

[JerseyJon]

I think it can be pretty easy to over analyze some tasks. .

Me??? Over analyze??? Bite your tongue.

Actually the real reason why I didn't use the little plastic valves was because the directions didn't mention them, and I looked at them and thought, "these are nice little valves. I wonder what they are for?"

So it wasn't a case of paralysis by analysis. It was a case of "duh".

[natemoen]

Those "factory calibrated" gauges need to be recalibrated to each other.

[motoman]

Don't forget.....................large fan in front of motor while adjusting and syncing!...............

[CatatonicBug]

Those "factory calibrated" gauges need to be recalibrated to each other.

Very good point! If you're using separate gauges, you need to connect each one to the same port, one at a time, and calibrate them all so they are all reading the same number from that one port.

[JerseyJon]

An update

Very good point! If you're using separate gauges, you need to connect each one to the same port, one at a time, and calibrate them all so they are all reading the same number from that one port.

So this past saturday, I synched the carbs just fine. I used the 4 gauge tool. The little plastic valves tamped down the needle flutter just fine. I will admit, however, that I did NOT calibrate the gauges before using them. Also, I got them pretty close to eachother during the synching process, but not exact.

I spent the next day riding all day. The bike ran with good power across all rpms.

The only negative is that I'm getting some backfiring I believe out of the left pipe. So there's something going on in 1 and 2. Any thoughts? Do I just need to sync better? Or could it be a timing issue. I have a small exhaust leak, but that's on the right side, sort of under the oil pan where there's a clamp.